Another important thing (for me at least) which is probably so obvious that it might not be worth mentioning: anyone working in your booth should be WEARING your jewelery, as many types as you sell. If you sell earrings, necklaces, bracelets, rings and ankle bracelets, you should be wearing at least one of each. It make a big difference to me.
And to echo what others have said: dark fabric on a board at an incline. Black velvet is pretty standard. Earrings hanging. Bracelets maybe on a fabric covered tube (like a sideways paper towel tube) would probably work.
And I would expect those small ziploc type bags for each individual piece after I buy it if you don't provide boxes with the cotton padding stuff(which I would rather get). I'm not going to be happy if I buy a ring and two necklaces and you toss them into one bag together.